I usually only go 3 zones far on the first day. The advantages are
- No water or food needed, means 1 more space in the inventory
- Easy rescue if there are too many zombies
- If you still need to build something that day, you have still water left
There are 12 zones that are 3 AP away from town and 8 that are 2 AP from town.
If you start directly after the nightly zombie attack you should be able to empty a zone alone by autosearching. If people start later they can share a zone.
The zones 1 AP away from the town are emtpied quickly by passing travelers, no need to have someone stay there. The zones 2 AP away have some people passing through them, but not enough to necessarily empty them on the first day. There are also 2 possible routes to each 3 AP zone, so if you get everyone to take the same ones you have another 4 zones were you can post people.
This means there are 16 easily reachable zones that can be emptied by 1 or 2 people. If someone gets stuck due to zombies it is easy to get them back with minimal AP waste as they are still near the town.
More experience players should try to find some buildings and go either 12 or 18 AP away from town, either alone if they are scouts or in small groups if they are citizens. This is best achieved by people who already know each other and are in a coalition.
The hard part is getting most people to follow your plan, you would need to be very early in the town and get the people on board. I don't think it is necessary to assign one zone to everyone, it probably is enough if people check which are currently free and choose one themselves.
This is mostly theory, I have never tried organizing the early scavenging like that. This is more of a base for discussions than a tried plan.